The field of this invention relates to the mechanized harvesting of horticultural crops. Of particular interest is the harvesting of fruit from fully dwarfed and semidwarf trees, and especially apple trees grown in hedgerow orchards.
The recent trend in orchard plantings has been toward the smaller varieties of trees. With the fully dwarfed and semidwarf trees, higher yields per acre are possible. They also lend themselves to rapid harvesting methods, particularly for mechanized systems. Another advantage lies in their ability to bear fruit in the first year of growth. This reduces the nonproductive time of a newly established orchard, and permits the grower to rapidly change from one variety of fruit to another as market demands dictate. Moreover, during the harvesting operation, the shorter distance the fruit drops lessens the likelihood of damage. This increases the overall quality of the fruit and the yield for fresh market use.
The trend in orchard planting has also been toward the hedgerow or tree wall concept. It is recognized by Arnold G. Berlage et al. ("Modifying Tree Fruit Culture to Engineering Needs," ASAE Presentation, Spokane, Washington, Oct. 18-20, 1967) that with regard to machine operation, straight line continuous motion is simplest and most efficient. This suggests that the ideal orchard should provide a continuous or unbroken fruiting surface to the harvesting machine. It has also been observed that if the foliage thickness of each row of trees is maintained no more than 5 to 6 feet, then the yield per acre and the harvestability of the fruit is maximized.
The importance of designing orchards for mechanical harvesting is the result of rapidly rising costs of field labor. Harvesting some fruits requires more hand labor than all the other growing operations combined, and thus has the most significant effect on the production costs. Mechanical harvesters could reduce these costs. Moreover, they are more reliable, give a fairly constant output, and can be operated in varying weather conditions. These factors are important as they allow the harvesting of the fruit at optimum maturity.
Since the advent of the mechanical fruit harvester, a variety of systems and designs have been developed. Many are discussed in "Mechanical Harvesting and Handling for Apples," Everett D. Markwardt et al. (ASAE Presentation, Technical Seminar on Implications or Mechanization for Fruit and Vegetable Harvesting, Chicago, Illinois, Dec. 8-10, 1968). Most devices were designed for use on standard-sized fruit trees and employ the shake-catch method. In this operation, the fruit is removed by a mechanical shaker clamped on the trunk or one of the scaffold limbs of the tree. It is then caught below on a catch frame.
The most popular shakers are of the inertia type and the impact type. These are described in detail in "Mechanical Harvesting Equipment for Deciduous Tree Fruits," R. B. Fridley and P. A. Adrian (California Agricultural Experiment Station Bulletin 825, University of California, Davis, July 1966). The basic principle of the inertia shaker is the transmission to the tree of reactive forces developed by an oscillating mass attached to the tree. In the impact type, a padded head in one end of a tube is pushed against a limb by a piston accelerated up the tube by compressed air. Both have proven effective to varying degrees and are usually mounted on a hydraulically operated boom affixed to a tractor or to the catching frame itself. In operation, the tractor is driven up to the tree and stopped; the shaker is maneuvered into position, clamped to the tree, and activated; after the fruit is collected, the shaker is removed from the tree and advanced to the next.
A wide variety of catching frames have been used with these shakers. Their purpose is to cushion the fall of the fruit to minimize bruising. They are normally made of a durable fabric, such as canvas, and have sloping deflector wings to move the fruit to a conveyor for transport to pallet boxes. Most are mobile and comprise two opposing sections which overlap when positioned under the tree from either side. In one embodiment, the entire canvas collecting area is covered with multiple tiers of decelerating strips. These strips minimize bruising by protecting fruit already on the canvas. Millier et al. (ASAE Paper No. 72-651, ASAE, St. Joseph, Missouri, 1972) teaches an air-bag catching surface. It utilizes a multilevel catching finger unit that extends into the trees and is inflated before the tree is shaken. Another type operates in conjunction with a high velocity air stream to float the fruit down to the catching device.
Catch frames are generally designed to channel the fallen fruit either directly into pallet boxes or to conveyors for conducting the fruit to the boxes. When the boxes are filled, they are replaced with empty ones and are eventually fork-lifted from the orchard.
Disadvantages of the standard shake-catch method are numerous, particularly when operated in modern hedgerow orchards where the tree density is 5-10 times that of the standard tree orchards. The discontinuity of the process as described above is time-consuming and inefficient. It normally takes 5-10 minutes to harvest a single tree. The large size of the shaker head makes it difficult to attach it to the tree trunk either above or below the catching frame. The frames themselves are bulky and difficult to maneuver in the narrow aisles. The slope of the deflector sings required for positive movement of the fruit to the conveyor and boxes often results in the outer edge of the frame being quite high off the ground and interfering with lower limbs. Pruning of these limbs reduce productivity of the tree. Moreover, transferring of the fruit from the catching frame to the pallet boxes results in further bruising and marked reduction in fruit quality. Exchanging the filled pallet boxes for empty ones and maneuvering the filled boxes in the narrow aisles for removal from the orchard have proven to be difficult and time-consuming. Finally, repair and maintainance of the pallet boxes is very costly.
Various sytems were designed specifically for harvesting in hedgerow orchards and eliminated some of the shake-catch deficiencies. Berlage et; a. (ASAE Paper No. 74-1522, ASAE, St. Joseph, Missouri, 1974) experimented with an over-the-row harvester equipped with a tree canopy. In operation, the canopy was enclosed and filled with plastic foam spheres to prevent bruising during the detaching and collecting of the fruit. The apples were harvested with a conventional trunk shaker, and the fruit and plastic foam spheres were separated. The concept required stopping, filling, collecting, and separating at each tree. Tests indicated that the time could be speeded up by eliminating the use of the spheres with not much sacrifice in the fruit quality. However, the discontinuity required in positioning the shaker on each tree, and the problem of dealing with the filled pallet boxes, still rendered the operation very inefficient.
In an attempt to device a continuous system, Tennes ("Evaluation of a Mechanical Over-the-Row Fruit Harvester," sponsored by Koehring Company, Harvey Harvester Division, 17237 Van Wagoner Road, Spring Lake, Michigan) tested in blueberry harvester on fruit trees. The machine employed a pair of rotating heads, each having 48 protruding "fingers" or tines for beating the foliage and knocking off the fruit. However, damage to the fruit, limbs, and bark of the trees was considerable. Lower rotation speeds lessened the damage and also the effectiveness of fruit removal. Other experimental systems for continuous harvesting from hedgerow trees are the pulsating air blast technique and the trellis wire method. The air blast system is described by Berlage et al. (ASAE Paper No. 74-1522, supra) and operates on the principle of knocking the fruit from the trees by pulsating jets of air. The air generating system is conveniently mounted in a straddle harvester equipped with a catching frame. In the trellis wire system, the trees are trained on a trellis wire similar to that for grape vines. The fruit is removed by shaking the wire and catching the fruit on a collecting surface below. These systems have also proven to be relatively ineffective for high yield removal and still suffer from the problems associated with pallet boxes.